A liquid chemical pump is employed in a liquid chemical usage process of a semiconductor manufacturing device in order to apply a predetermined quantity of liquid chemical to a semiconductor wafer. One liquid chemical pump that is known has a pump chamber filled with liquid chemical, and an operation chamber that introduces operating air, which are separated by a flexible membrane such as a diaphragm, and the flexible membrane is deformed by adjustably setting the air pressure inside the operation chamber in order to draw in and discharge the liquid chemical (see, for example, Japan Published Patent Application No. H11-343978).
In a liquid chemical supply system in which the liquid chemical pump described above is employed, the control precision of the liquid chemical discharge flow rate is improved by controlling the air pressure inside the operation chamber with high precision. More specifically, the air pressure is detected by a pressure sensor, and feedback control is performed so as to match the detected pressure with a target pressure setting value.
In addition, the liquid chemicals supplied by the liquid chemical supply system have various fluid viscosities, and it is thought that the control precision of the discharge flow rate is influenced by the different fluid viscosities of the liquid chemicals. When the control precision of the discharge flow rate changes in response to the type, etc. of liquid chemical, the quality of the product, such as the semiconductor wafer, may be influenced thereby.